as soon as you use JSF component for repetition (a4j:repeat, ui:repeat), the only option for you is inserting the line as a < img > (or a symbol). In case of using non-JSF repetitions (c:forEach or from the java code), you can have much more options.
How would I do it using java code for more options?
using itemSeparator="line" of the toolBarGroup.
In java code, you need to add each s:link as a direct child of toolBarGroup. Currently, you have a a4j:repeat as a only one child for toolBarGroup. So, itemSeparator does not make sense.
The same will work in case of using c:forEach
Ah. You know, I never knew that you could use core functions in JSF. then I found out there's a separate TLD for non JSP use. So it's working now. Thanks!